It is well-known in the art that aluminosilicate zeolites can be composited with a matrix or a binder material in order to impart strength thereto. Alumina is a well-known and cheap binder material and is often used in commercially developed zeolite systems. It appears, as acknowledged in EP-A-0167324, that it is much more difficult to use silica as binder for aluminosilicate zeolites if one is to take advantage of the inherent properties of silica as a catalyst (co)carrier beyond the techniques of filling or pelletising.
In said EP-A-0167324, it is described that both silica and mixtures of silica and aluminosilicate zeoliters can be extruded when using an alkali metal compound such as sodium hydroxide or sodium carbonate in a total solids content of from 25% to 75% by weight, the alkali compound being added in an amount of from 0.25 to 10% by weight on a dry basis, based on total solids content of the mixture. The crush strength of materials thus extruded appears to have increased substantially.
The choice of an alkali compound as extrusion aid is rather specific in that it is stated emphatically in the above European patent specification that ammonium hydroxide is not effective but that more basic quaternary ammonium hydroxides can be used although they are not preferred because of a tendency to produce thixotropic masses which are difficult to extrude as well as the fact that they are relatively expensive.
It appears, however, that the use of an alkali compound as an extrusion aid for aluminosilicate zeolite containing systems has a severe drawback in that it substantially damages the crystallinity of crystalline aluminosilicate zeolites having a relatively high silica-alumina molar ratio. This holds both for crystalline aluminosilicate zeolites prepared as such or which have been subjected to one or more dealumination procedures known to those skilled in the art.
It has now been found that a certain class of alkanolamines can be suitable applied to produce extrudates containing silica and dealuminated aluminosilicate zeolites wherein the aluminosilicate zeolites have retained no less than 90% of their initial crystallinity which renders such extrudates particularly attractive for the production of various types of, inter alia, hydroprocessing catalysts.